/*
 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.script;

import java.io.Reader;
import java.util.Map;
import java.util.Set;

/**
 * <code>ScriptEngine</code> is the fundamental interface whose methods must be
 * fully functional in every implementation of this specification.
 * <br><br>
 * These methods provide basic scripting functionality.  Applications written to this
 * simple interface are expected to work with minimal modifications in every implementation.
 * It includes methods that execute scripts, and ones that set and get values.
 * <br><br>
 * The values are key/value pairs of two types.  The first type of pairs consists of
 * those whose keys are reserved and defined in this specification or  by individual
 * implementations.  The values in the pairs with reserved keys have specified meanings.
 * <br><br>
 * The other type of pairs consists of those that create Java language Bindings, the values are
 * usually represented in scripts by the corresponding keys or by decorated forms of them.
 *
 * @author Mike Grogan
 * @since 1.6
 */

public interface ScriptEngine {

  /**
   * Reserved key for a named value that passes
   * an array of positional arguments to a script.
   */
  public static final String ARGV = "javax.script.argv";

  /**
   * Reserved key for a named value that is
   * the name of the file being executed.
   */
  public static final String FILENAME = "javax.script.filename";

  /**
   * Reserved key for a named value that is
   * the name of the <code>ScriptEngine</code> implementation.
   */
  public static final String ENGINE = "javax.script.engine";

  /**
   * Reserved key for a named value that identifies
   * the version of the <code>ScriptEngine</code> implementation.
   */
  public static final String ENGINE_VERSION = "javax.script.engine_version";

  /**
   * Reserved key for a named value that identifies
   * the short name of the scripting language.  The name is used by the
   * <code>ScriptEngineManager</code> to locate a <code>ScriptEngine</code>
   * with a given name in the <code>getEngineByName</code> method.
   */
  public static final String NAME = "javax.script.name";

  /**
   * Reserved key for a named value that is
   * the full name of Scripting Language supported by the implementation.
   */
  public static final String LANGUAGE = "javax.script.language";

  /**
   * Reserved key for the named value that identifies
   * the version of the scripting language supported by the implementation.
   */
  public static final String LANGUAGE_VERSION = "javax.script.language_version";


  /**
   * Causes the immediate execution of the script whose source is the String
   * passed as the first argument.  The script may be reparsed or recompiled before
   * execution.  State left in the engine from previous executions, including
   * variable values and compiled procedures may be visible during this execution.
   *
   * @param script The script to be executed by the script engine.
   * @param context A <code>ScriptContext</code> exposing sets of attributes in different scopes.
   * The meanings of the scopes <code>ScriptContext.GLOBAL_SCOPE</code>, and
   * <code>ScriptContext.ENGINE_SCOPE</code> are defined in the specification. <br><br> The
   * <code>ENGINE_SCOPE</code> <code>Bindings</code> of the <code>ScriptContext</code> contains the
   * bindings of scripting variables to application objects to be used during this script
   * execution.
   * @return The value returned from the execution of the script.
   * @throws ScriptException if an error occurs in script. ScriptEngines should create and throw
   * <code>ScriptException</code> wrappers for checked Exceptions thrown by underlying scripting
   * implementations.
   * @throws NullPointerException if either argument is null.
   */
  public Object eval(String script, ScriptContext context) throws ScriptException;


  /**
   * Same as <code>eval(String, ScriptContext)</code> where the source of the script
   * is read from a <code>Reader</code>.
   *
   * @param reader The source of the script to be executed by the script engine.
   * @param context The <code>ScriptContext</code> passed to the script engine.
   * @return The value returned from the execution of the script.
   * @throws ScriptException if an error occurs in script.
   * @throws NullPointerException if either argument is null.
   */
  public Object eval(Reader reader, ScriptContext context) throws ScriptException;

  /**
   * Executes the specified script.  The default <code>ScriptContext</code> for the
   * <code>ScriptEngine</code> is used.
   *
   * @param script The script language source to be executed.
   * @return The value returned from the execution of the script.
   * @throws ScriptException if error occurs in script.
   * @throws NullPointerException if the argument is null.
   */
  public Object eval(String script) throws ScriptException;

  /**
   * Same as <code>eval(String)</code> except that the source of the script is
   * provided as a <code>Reader</code>
   *
   * @param reader The source of the script.
   * @return The value returned by the script.
   * @throws ScriptException if an error occurs in script.
   * @throws NullPointerException if the argument is null.
   */
  public Object eval(Reader reader) throws ScriptException;

  /**
   * Executes the script using the <code>Bindings</code> argument as the <code>ENGINE_SCOPE</code>
   * <code>Bindings</code> of the <code>ScriptEngine</code> during the script execution.  The
   * <code>Reader</code>, <code>Writer</code> and non-<code>ENGINE_SCOPE</code>
   * <code>Bindings</code> of the default <code>ScriptContext</code> are used. The
   * <code>ENGINE_SCOPE</code> <code>Bindings</code> of the <code>ScriptEngine</code> is not
   * changed, and its mappings are unaltered by the script execution.
   *
   * @param script The source for the script.
   * @param n The <code>Bindings</code> of attributes to be used for script execution.
   * @return The value returned by the script.
   * @throws ScriptException if an error occurs in script.
   * @throws NullPointerException if either argument is null.
   */
  public Object eval(String script, Bindings n) throws ScriptException;

  /**
   * Same as <code>eval(String, Bindings)</code> except that the source of the script
   * is provided as a <code>Reader</code>.
   *
   * @param reader The source of the script.
   * @param n The <code>Bindings</code> of attributes.
   * @return The value returned by the script.
   * @throws ScriptException if an error occurs.
   * @throws NullPointerException if either argument is null.
   */
  public Object eval(Reader reader, Bindings n) throws ScriptException;


  /**
   * Sets a key/value pair in the state of the ScriptEngine that may either create
   * a Java Language Binding to be used in the execution of scripts or be used in some
   * other way, depending on whether the key is reserved.  Must have the same effect as
   * <code>getBindings(ScriptContext.ENGINE_SCOPE).put</code>.
   *
   * @param key The name of named value to add
   * @param value The value of named value to add.
   * @throws NullPointerException if key is null.
   * @throws IllegalArgumentException if key is empty.
   */
  public void put(String key, Object value);


  /**
   * Retrieves a value set in the state of this engine.  The value might be one
   * which was set using <code>setValue</code> or some other value in the state
   * of the <code>ScriptEngine</code>, depending on the implementation.  Must have the same effect
   * as <code>getBindings(ScriptContext.ENGINE_SCOPE).get</code>
   *
   * @param key The key whose value is to be returned
   * @return the value for the given key
   * @throws NullPointerException if key is null.
   * @throws IllegalArgumentException if key is empty.
   */
  public Object get(String key);


  /**
   * Returns a scope of named values.  The possible scopes are: <br><br> <ul>
   * <li><code>ScriptContext.GLOBAL_SCOPE</code> - The set of named values representing global
   * scope. If this <code>ScriptEngine</code> is created by a <code>ScriptEngineManager</code>, then
   * the manager sets global scope bindings. This may be <code>null</code> if no global scope is
   * associated with this <code>ScriptEngine</code></li> <li><code>ScriptContext.ENGINE_SCOPE</code>
   * - The set of named values representing the state of this <code>ScriptEngine</code>.  The values
   * are generally visible in scripts using the associated keys as variable names.</li> <li>Any
   * other value of scope defined in the default <code>ScriptContext</code> of the
   * <code>ScriptEngine</code>. </li> </ul> <br><br> The <code>Bindings</code> instances that are
   * returned must be identical to those returned by the <code>getBindings</code> method of
   * <code>ScriptContext</code> called with corresponding arguments on the default
   * <code>ScriptContext</code> of the <code>ScriptEngine</code>.
   *
   * @param scope Either <code>ScriptContext.ENGINE_SCOPE</code> or <code>ScriptContext.GLOBAL_SCOPE</code>
   * which specifies the <code>Bindings</code> to return.  Implementations of
   * <code>ScriptContext</code> may define additional scopes.  If the default
   * <code>ScriptContext</code> of the <code>ScriptEngine</code> defines additional scopes, any of
   * them can be passed to get the corresponding <code>Bindings</code>.
   * @return The <code>Bindings</code> with the specified scope.
   * @throws IllegalArgumentException if specified scope is invalid
   */
  public Bindings getBindings(int scope);

  /**
   * Sets a scope of named values to be used by scripts.  The possible scopes are: <br><br> <ul>
   * <li><code>ScriptContext.ENGINE_SCOPE</code> - The specified <code>Bindings</code> replaces the
   * engine scope of the <code>ScriptEngine</code>. </li> <li><code>ScriptContext.GLOBAL_SCOPE</code>
   * - The specified <code>Bindings</code> must be visible as the <code>GLOBAL_SCOPE</code>. </li>
   * <li>Any other value of scope defined in the default <code>ScriptContext</code> of the
   * <code>ScriptEngine</code>. </li> </ul> <br><br> The method must have the same effect as calling
   * the <code>setBindings</code> method of <code>ScriptContext</code> with the corresponding value
   * of <code>scope</code> on the default <code>ScriptContext</code> of the
   * <code>ScriptEngine</code>.
   *
   * @param bindings The <code>Bindings</code> for the specified scope.
   * @param scope The specified scope.  Either <code>ScriptContext.ENGINE_SCOPE</code>,
   * <code>ScriptContext.GLOBAL_SCOPE</code>, or any other valid value of scope.
   * @throws IllegalArgumentException if the scope is invalid
   * @throws NullPointerException if the bindings is null and the scope is
   * <code>ScriptContext.ENGINE_SCOPE</code>
   */
  public void setBindings(Bindings bindings, int scope);


  /**
   * Returns an uninitialized <code>Bindings</code>.
   *
   * @return A <code>Bindings</code> that can be used to replace the state of this
   * <code>ScriptEngine</code>.
   **/
  public Bindings createBindings();


  /**
   * Returns the default <code>ScriptContext</code> of the <code>ScriptEngine</code> whose Bindings,
   * Reader and Writers are used for script executions when no <code>ScriptContext</code> is
   * specified.
   *
   * @return The default <code>ScriptContext</code> of the <code>ScriptEngine</code>.
   */
  public ScriptContext getContext();

  /**
   * Sets the default <code>ScriptContext</code> of the <code>ScriptEngine</code> whose Bindings,
   * Reader and Writers are used for script executions when no <code>ScriptContext</code> is
   * specified.
   *
   * @param context A <code>ScriptContext</code> that will replace the default
   * <code>ScriptContext</code> in the <code>ScriptEngine</code>.
   * @throws NullPointerException if context is null.
   */
  public void setContext(ScriptContext context);

  /**
   * Returns a <code>ScriptEngineFactory</code> for the class to which this
   * <code>ScriptEngine</code> belongs.
   *
   * @return The <code>ScriptEngineFactory</code>
   */
  public ScriptEngineFactory getFactory();
}
